Electrostatic spray assembly

ABSTRACT

An electrostatic spraying assembly including a housing and a plurality of elongated electrode elements supported within the housing each defining a respective fluid passageway. An electrode header connectable to a high voltage source is supported within the housing in spaced relation to the electrode elements for charging the electrodes to an electrical potential by induction, and in turn, charging liquid directed through the passageways. The electrode header and a resilient valve element supported thereon are movable between retracted and closing positions for controlling the flow of fluid through the electrode passageways for discharge into an electrical field generated by an induction element supported in spaced relation to the discharge ends of the electrode elements.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication No. 60/733,289 filed Nov. 3, 2005, and is acontinuation-in-part of application Ser. No. 11/056,703 filed Feb. 11,2005, which in turn claims the benefit of U.S. Provisional PatentApplication No. 60/544,269 filed on Feb. 12, 2004, the disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to spray nozzle assemblies, andmore particularly, to electrostatic spray nozzle assemblies thatelectrostatically charge fluids discharging from spray nozzles tofacilitate liquid particle breakdown and distribution.

BACKGROUND OF THE INVENTION

Electrostatic spray nozzle assemblies are utilized for applying oil andother coating and lubricating fluids in various manufacturing processes.Electrostatic spray nozzle assemblies, such as shown in U.S. Pat. No.4,749,125, discharge a plurality of fluid flow streams which areelectrostatically charged and atomized by means of a high voltageelectrode with the assistance of a grounded induction bar fordisposition onto items to be sprayed or coated, typically as they areconveyed past the spraying apparatus.

Heretofore, such electrostatic assembly spray nozzle assemblies havesuffered from various operating and maintenance problems. For example,imprecise manufacture and assembly of such spray nozzles and chargingelectrodes can result in high voltage leakage that can significantlyaffect the operating efficiency of the spray operation. Fluid leakageproblems also can adversely affect the spray distribution and lead towaste of costly spray liquids. While it often is desirable to direct aplurality of electro-statically charged flow streams, heretofore it hasbeen difficult to effectively and efficiently control the liquiddischarge for cyclic operation and without undesirable dripping andwaste of the coating fluid.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide an electrostaticspray nozzle assembly that is adapted for more efficient and reliablespraying of oils and other lubricating and coating fluids.

Another object is to provide an electrostatic spray nozzle assemblywhich includes electrostatic charging electrodes that are adapted formore precise manufacture and mounting within the nozzle assembly, andhence more efficient operation with reduced power consumption andincreased life expectancy.

A further object is to provide an electrostatic spray nozzle assembly ofthe foregoing type which is operable for electrostatically charging andcontrolling the spray discharge of a plurality of fluid flow streams formore uniform coating or lubricating of items that are sprayed.

Still another object is to provide an electrostatic spray nozzleassembly of the above kind that can be efficiently controlled forrepeated cyclic operation without undesirable drippage during shut-off.

Another object is to provide an electrostatic spray nozzle assembly thathas relatively large fluid passages that resist clogging and are easy toclean.

Yet a further object is to provide such an electrostatic spray nozzleassembly which is relative simple in construction and lends itself toeconomical manufacture.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative spray nozzle assembly inaccordance with the invention; and

FIG. 2 is an enlarged vertical section of the illustrated spray nozzleassembly taken in the plane of line 2-2 in FIG. 1, showing the spraynozzle assembly in an operating condition;

FIG. 3 is an enlarged longitudinal section, taken in the plane of line3-3 in FIG. 1, again showing the spray nozzle assembly in an operatingcondition; and

FIG. 4 is an enlarged fragmentary section, showing the spray nozzleassembly in a liquid shut-off condition.

While the invention is susceptible of various modifications andalternative constructions, a certain illustrated embodiment thereof hasbeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific form disclosed, but on the contrary, theintention is to cover all modifications, alternative constructions andequivalents falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now more particularly to the drawings, there is shown in anillustrative electrostatic spray nozzle assembly 10 embodying thepresent invention, which is adapted for directing an elongated spray ofoil or other lubricating or coating fluid on items conveyed below thespray assembly 10. The illustrative spray assembly 10 basicallycomprises a non-metallic elongated housing 11 having an inlet portconnected to a fluid supply pipe 12 that supplies liquid coating orother fluid materials to the spray assembly 10, an electrode assembly 14within the spray housing 11 for charging fluid passing through anddirected from a lower discharge end of the housing 11, and an inductionbar 15 disposed in parallel spaced relation to the discharge end of thehousing 11 for generating an electrical field to enhance liquid particlebreakdown. It will be appreciated that the housing 11 may beappropriately supported by support brackets or the like in overlyingrelation to items to be sprayed.

In accordance with the invention, the electrode assembly comprises ametallic block or header and a plurality of elongated electrode elementsdisposed in alignment with respective fluid passageways communicatingwith the fluid inlet port of the housing for charging fluid as it passesalong the length of the elongated electrode elements and is dischargedfrom the spray assembly. To this end, in the illustrated embodiment, theelectrode assembly 14 comprises an elongated metallic electrode block 14a disposed within a relatively larger sized channel 15 within thehousing 11 and a plurality of elongated electrode elements 14 bsupported in a longitudinally spaced array in depending relation to thehousing 11. The rectangular channel 15 of the housing in this case issized larger than the electrode block 14 a for defining an elongatedgenerally U-shaped fluid flow passageway 16 (FIG. 4) communicatingbetween the fluid inlet port and each of the elongated electrodeelements 14 b. For enclosing the upper end of the elongated channel 15,the housing 11 has a cover 18 which is secured to the upper end of thehousing by appropriate fastening bolts 19 with a sealing gasket 20interposed there between. The electrode block 14 a is connected to anappropriate high voltage source, such as 20,000 volt source, by means ofa conventional banana coupling 21 coupled to the electrode block 14 a ata central location through a side wall of the housing 11. As will becomeapparent to a person skilled in the art, by reason of the high voltagecharged electrode block 14 a, the adjacent row of elongated electrodeelements 14 b will be charged by induction to a sufficiently highelectrical potential for charging fluid as it passes along the length ofthe electrode elements 14 b and is discharged from the spray assembly.

In carrying out the invention, the elongated electrode elements are inthe form of elongated metallic tubes which each define a respectiveliquid flow passageway communicating between the internal housing fluidpassageway 16 and simultaneously charge the liquid as it is passingthrough the electrode tubes 14 b. As will be understood by a personskilled in the art, as the fluid passes through the electrode tubes 14b, it is charged such that when the fluid exits the tubes 14 b andenters the electrical field between the terminal ends of the tubes 14 band the induction bar 15, fluid is dispersed in a fine particle spray.The use of the electrode tubes 14 b also provide relatively large flowpassages that are more resistant to clogging and are easier to clean.

The electrode tube receiving body of the housing 11 preferably has aone-piece block construction which facilitates precision concentricmounting of the electrode tubes 14 a for preventing high voltageleakage. The illustrated housing 11 includes a one-piece body 24,preferably machined from plastic stock, with electrode tube receivingopenings being drilled in the body and the longitudinal channel 15 beingmilled. It will be understood that by virtue of such one-piece housingbody construction, there are no parting planes associated with theliquid flow passageways 16 typical of multi-part housings, nor fastenersfor retaining a multi-part housing body in assembled condition at suchparting planes.

The electrode tubes 14 a preferably each protrude outwardly of thedischarge end of the housing 11 a predetermined distance “x,” such asabout ¼ inch (see FIG. 2). It has unexpectedly been found that theprotruding electrode tubes maximize liquid flow rate through the spraynozzle assembly. Although the theory of operation is not entirelyunderstood, it is believed that the greater surface area of tubes overwhich the liquid travels facilitates liquid flow and discharge from thespray nozzle assembly. The increased contact with the electrode tubesfurther enhances charging of the liquid and ultimate atomization. Thehousing 11 in this case is formed with a generally tapered depending endthrough which the electrode tubes 14 b protrude for further preventingthe effect of possible surface tension on the liquid as it dischargesfrom the housing.

To enhance safety, the electrode tubes 14 b preferably are arranged suchthat each tube terminates a small distance S (FIG. 4) from the electrodeblock or header 14 a which in this case places the upper ends of thetubes 14 b in slightly recessed relation the upper perimeter of thehousing bores within which the tubes are mounted. With this arrangement,the electrode tubes 14 b will not be charged at such high electricalpotential that could pose a safety hazard. Instead, the electrode tubes14 b are charged inductively due to their proximity to the electrodeheader 14 a. The inductive charging of the electrode tubes 14 b willprovide sufficient charging to provide the desired level of added chargeto the fluid passing through the tubes 14 b. Accordingly, safety of thespray operation is increased without significant degradation in sprayperformance.

The induction bar 15 in this case is mounted for selective positioningrelative to the downstream ends of the electrode tubes 14 b formaximizing the effect of the electrical field therebetween on thedischarging liquid, and hence, maximizing liquid particle breakdown. Asshown in FIG. 1, the induction bar 15, is supported by elongated arms 26fixed in depending angled relation to opposite ends of the housing 11.The induction rod 15 is selectively positionable within elongated slots28 formed in the supporting arms 26 for effecting the desired spraycharacteristics.

In operation of the spray assembly 10, it will be seen that oil or otherlubricating or coating fluid may be supplied through the liquid supplypipe 12 into communication with the longitudinal flow channel 16 andthrough the plurality of longitudinally spaced depending electrode tubes14 b, being charged along their entire length of travel. Upon dischargefrom the electrode tubes into electrical field 23 between the electrodetubes 14 b and the induction ban 5, the liquid is dispersed into a fineparticle spray with the repelling charges of the particles effectingsubstantially uniform distribution onto items to be coated positioned aspassing below the spray assembly 10.

In carrying out a further important aspect of the invention, the spraynozzle assembly 10 is adapted for efficient cyclic operation withoutundesirable dripping or wastage of liquid. To this end, the underside ofthe electrode block 14 a is provided with a valve element in the form ofan elongated sealing gasket 30 and the electrode block 14 b is moveablebetween a raised operating position that permits the flow of fluidthrough the housing and to each of the electrode tubes 14 b, as depictedin FIGS. 2 and 3, and a lowered closed position in which the elongatedsealing gasket 30 simultaneously closes the inlets to each of theelectrode tubes 14 b as depicted in FIG. 4. The sealing gasket 30 inthis case has a generally cylindrical upper portion 31 which is pressfit within to a complimentary recess in the underside of the electrodeblock 14 a and a lower generally rectangular portion 32 that defines aflat sealing surface for contacting the flat bottom of the housingchannel in overlying relation to the cylindcrical bores thatcommunicates with electrode tubes 14 b. For raising and lowering theelectrode block 14 a and sealing gasket 30 between such operating andclosed positions, a pair of air cylinders 35 are mounted in the upperend of the housing cover 18 which each have a respective cylinder rod 35a threadedly fixed to the electrode block 14 a. The cylinders may be ofa known spring return type, such that upon pressurized air actuation thepiston and rod thereof are raised against the biasing force of thereturn spring and upon deactuation of the pressurized air supply, thecylinder return springs force the piston rods 35 a, electrode block 14a, and gasket 30 to the lowered position simultaneously interrupting thecommunication of fluid to the electrode tubes 14 b.

In carrying out the invention, to permit such raising and lowering ofthe electrode block 14 a within the housing channel 15 while maintainingthe electrode block in conductive relation to the banana coupling 21,the electrode block 14 a is formed with an elongated slot 38, whichreceives a conductive rod 39 of the banana coupling 21 (FIG. 3). Theslot 38 has a vertical length sufficient to permit movement relative tothe conductive rod 39 during raising and lowering movement of theelectrode block 14 a and a width corresponding substantially to thewidth of the rod 39 for maintaining electrical contact with theconductive rod 39.

It has been found that by virtue of the simultaneous opening andshutting of the electrode tubes to the supply of fluid at locationsadjacent their inlet ends, the spray nozzle assembly 10 can beefficiently operated with reliable drip-free termination of spraying.The air cylinders further permit easy control and reliable operation.Yet the spray nozzle assembly 10 is relatively simple in constructionand lends itself to economical manufacture.

1. An electrostatic spraying assembly comprising; a housing, a pluralityof an elongated electrode elements supported in said housing, saidhousing having a fluid inlet passage that is connectable to a fluidsource and a fluid passage communicating between said fluid inlet andsaid electrode elements, said electrode elements each having a fluidpassageway with an upstream inlet end communicating with said housingfluid passage and an outlet end through which fluid can be discharged,an electrode header within said housing connectable to a voltage sourcefor electrically-charging said electrode elements and fluid passingthrough said electrode element passageways, and a value element movablebetween a retracted position that permits passage of fluid through saidhousing passage and said electrode elements fluid passageways duringwhich time said fluid is electrically charged and a closing positionthat prevents passage of fluid through said electrode element dischargepassageways.
 2. The electrostatic spraying system of claim 1 in whichsaid valve element is a part of said electrode header, and saidelectrode header being movable between said closing and retractedpositions.
 3. The electrostatic spraying system of claim 1 in which saidelectrode header is disposed within said housing in spaced relation tothe upstream inlet ends of said electrode elements for charging saidelectrodes to an electrical potential by induction.
 4. The electrodespraying assembly of claim 1 in which each said electrode element ismounted within a respective passageway in said housing, and saidupstream inlet end of each electrode elements being disposed in recessedrelation below an upstream end of the respective housing passageway. 5.The electrostatic spraying system of claim 1 in which said housingincludes a one-piece plastic body formed with a chamber for receivingthe electrode header, and a cover positionable in sealed relation ontosaid body enclosing said chamber.
 6. The electrostatic spraying assemblyof claim 1 in which said electrode elements are arranged in a row, andsaid valve element has an elongated configuration for simultaneouslypreventing passage of liquid through the discharge passageways of saidelectrode elements when in said closing position.
 7. The electrostaticspraying assembly of claim 2 in which said valve element is a sealingmember mounted on said electrode header, and said electrode header andsealing member are movable between said retracted and closing positions.8. The electrostatic spraying system of claim 7 in which said sealingmember has a generally cylindrical mounting end disposed within acomplementary recess in an underside of said electrode header and alower generally rectangular portion that defines a sealing surface forclosing the inlet ends of said electrode elements when in a closingposition.
 9. The electrostatic spraying system of claim 6 including atleast one cylinder for cyclically raising and lowering said electrodeheader and sealing member between said open and closed positions. 10.The electrostatic spraying system of claim 1 in which electrode headeris arranged within said housing liquid passage.
 11. The electrostaticspraying assembly of claim 2 including a coupling element for connectingsaid electrode header to said voltage source, and said electrode headerbeing movable relative to said coupling element during movement betweensaid retracted and closing positions.
 12. The electrostatic sprayingassembly of claim 11 in which said electrode header has an elongatedslot within which said coupling element is positioned in electricalcontact with said header, and said coupling element is slidable withinsaid slot during movement of said header between said retracted andclosing positions for maintaining electrical contact with the electrodeheader.
 13. The electrostatic spraying system of claim 1 in which theoutlet ends of said electrode elements protrude a predetermined distanceoutwardly of said housing.
 14. The electrostatic spraying system ofclaim 11 in which said housing is formed with a tapered discharge endfrom which the outlet ends of said electrode elements protrude.
 15. Theelectrostatic spraying system of claim 1 further including an inductionelement supported in spaced relation to the outlet ends of saidelectrode elements for generating an electrical field between thedischarge ends of said electrode elements and said induction bar intowhich discharging fluid is dispersed.